Polishing compositions



Patented May 15, 1945 Albert Saunders, Maplewood, and Loy S. Engle,

Harrington Park, N. .L, assignors to Interchemical Corporation, NewYork, N. Y., a corporation of Ohio No Drawing. Original applicationOctober 16,

1941, Serial N0. 415,-212. Divided and this application April 19,1944,Serial No. 531,791

2 Claims. (01. 51-308) This invention relates to polishing compositionsand methods particularly useful in the elimination of blemishes in bakedresin finishes on automobile bodies and the like. In particular, itrelates to the use of certain calcium silicates as polishing agents forthis purpose.

In the past, the most common finish for automobile bodies has been athermoplastic coating such as nitrocellulose lacquer. In order to givesuch finishes a gloss surface, it is necessary to sand and polish them.While the polishing is an expensive process, it satisfactorily leads toa high gloss surface, probably because the plastic flow of the finishunder th heat of polishing eliminates the fine scratches which arenecessarily produced by the abrasives used. The blemishes or damagedplaces which occur not infrequently in the handling of automobile bodyparts may easily be-repaired and rendered indistinguishable from theremainder of the surface by sanding and polishing the patch in the sameway that the whole finish is sanded and polished.

Heat-hardened finishes, in which term we in cludev all those finishescontaining resins which are hardened rather than softened by theapplication of heat and are customarily baked after application toconvert the resin to the heathardened condition, have the advantage ofproviding gloss surfaces without sanding or polishing. For this reason,a considerable economy could be introduced by using such finishesinstead of thermoplastic finishes on automobile body parts, were it notfor the fact that no method of eliminating blemishes in baked resinfinishes has been known. Consequently, when baked resin finishes areused, any body part containing a blemish caused by scratching orchipping in handling must be completely refinished. This eliminates theeconomies which would otherwise be present in the use of baked resinfinishes.

The dimculty in patching baked resin finishes arises from the fact that,no matter how smooth the surface of the patch and the surface of themain body of the finish may be, the outline of the patch is clearlyvisible owing to the absence of a polishing operation on the non-patchedparts of the automobile body which would blend the patch with the mainbody of the finish as in the case of thermoplastic finishes. Attempts toeliminate the ,line of demarcation in patched baked resin finishes by apolishing operation have proved unsuccessful, for the fine scratchesformed by fine abrasive polishes are not eliminated by plastic flow asin the case of thermoplastic finishes, and the polishing, therefore,leaves a slightly hazy appearance differing from the loss appearance ofthe smooth unpolished surface of the main body of the finish. It has,heretofore, proved impossible to make the patch invisible.

However, the difference in appearance between polished and unpolishedareas of a baked resin finish may be eliminated without completelyeliminating the fine scratches caused by abrasive polishing material.The hazy appearance of the polished areas arises not merely from thepresence of fine scratches, but from the presence of debris or minuteparticles and shavings of the baked resin contained in the scratches. Itis this debris which scatters incident light and gives the appearance ofhaze. It is possible to eliminate the debris or shavings from thescratches, and thus to produce a finely scratched area which does notdiffer in appearance from. the unscratched and unpolished gloss areas ofthe surface by fiocculating the debris into agglomerations with theabrasive, which can be rubbed from the surface. This method of polishingforms the subject matter of a co-pending application of one of theco-inventors here with others, Serial Number 393,934, filed May 17,1941. e

As disclosed in the above application, comparatively few of the fineabrasive powders which are used as polishing agents have the property offiocculating with particles of baked resin. Those which have thisproperty may be selected and identified by the following test:

The abrasive powder to be tested is mixed with fragments (or a powder)of the resin of which the surface to be polished is made (or a resinousmaterial substantially identical therewith), and the mixture is wet withthe liquid to be used as the vehicle in applying the abrasive powder.Ordinarily, water is the most practical vehicle. The mixture is thenobserved through a microscope using a magnification of from todiameters. In case the particles of the mixture are seen to formagglomerations in the liquid, the abrasive powder is shown to have theproperty of fiocculating with the baked resin particles in the liquid.With respect to non-aqueous vehicles, the abrasive particles mightacquire, on preliminary mixing, an electrical charge oppo-. site to thatof the resin fragments, with consequent agglomeration of the materials.The materials may be redispersed by rubbing the par ticles unless theredispersion is opposed by the phenomenon of flocculation mentionedabove. This agglomeration due to electrical (or static) chargesmust notbe confused with the true flocculation phenomenon, as the former is nota identified patent application has been lack of stability on'storage ina vehicle. The polishing agents tend to react in aqueous media, toproduce materials which can no longer be successfully used in polishing.

Another difiiculty frequently encountered with these polishing agentshas been dusting of the polish on the bufiing wheels, apparently due totoo rapid drying of the aqueous vehicle.

This invention provides an inexpensive polishing composition which isstable on storage, and which at the same time will remove the haze fromnon-thermoplastic resinous finishes quickly. The composition includes anew abrasive material stable on storage in aqueous systems, and in itspreferred form it is combined with certain water-miscible vehicles. Theabrasive powder which contributes to the superior qualities of thispolishing composition is an alkalinereacting, precipitated, hydrated,calcium silicate.

Preferably, the calcium silicate is in finely divided form (averageparticle size under 1 micron). A typical product of this type isavailable in the market under the trade name "Silene," and ismanufactured by the Pittsburgh Plate Glass Company. This product has anapproximate analysis of:

Bulk density (powder) lbs./cu. ft.-- 15 to 16 Refractive index 1.463

Silene exhibits the flocculation with fragments of non-thermoplasticresins which is characteristic of abrasive powders capable of polishingthese resinous finishes, when subjected to the flocculation testdescribed above; but unlike hitherto available abrasive powders capableof producing optimum gloss, or freedom from haze, mixtures of Silene"with aqueous vehicles maintain their polishing properties on prolongedstanding.

Furthermore, results superior to any obtained with heretofore knownpolishing compositions can be obtained if the vehicle in which theSilene" is to be used is selected from a small and special group. Thevehicles which have been found to yield superior polishing compositionswith Silene," and hence are included in this invention, are ethyleneglycol, formamid and glycerol, and they are preferred in the order givenAlthough these three vehicles may be used undiluted with the Silene itis more economical to add water to the composition, and in some casesthe presence of water is beneficial.

The proportion of Silene to vehicle is not critical, the criterion beingthat of obtaining a smooth, easily workable paste. The compositions weretested by rubbing various resinous surfaces, such asphenol-formaldehyde, ureaalkyd, oleoresinous and alkyd, which had beendulled by rubbing with a fine abrasive, followed by rubbing withMcAleer's polish. The latter polish reduced the dullness left by theabrasive, but the resinous surfaces were still hazy or semimatte inappearance. After cleaning the surface with a hydrocarbon solvent toremove wax, they were rubbed with typical compositions made inaccordance with this invention until a highly glossy surface free fromhaze and exhibiting no visual difference from the rest of the finish wasproduced. These compositions are described in the following examples.

Example 1 A polishing composition was made by mixing- Parts by weightEthylene glycol '75 Silene" 33 Water may be added if desired, but thiscomposition produced the haze-free gloss with least rubbing or laborwithout dilution.

Example 2 This polish produced the desired gloss with the least laborand in the least time of all of the polishes, when used on a urea-alkydresin baked finish, but it was not as satisfactory as the composition ofExample 1 when used on other resinous surfaces.

' Example 3 The polishing composition consisted of- Parts by weightGlycerol 37.5 Water 12.5 Silene 23.0

This polish quickly removed the haze from the resinous surfaces, but itwas not quite as efllcient as the polish of Example 1.

The .Silene was tried with numerous other vehicles and combinations ofvehicles, and with nearly all of them results were obtained which weresuperior to those obtainable with other abrasives or powders in the samevehicles In particular, the Silene" .could be successfully used withwaxes wherein the vehicle was in the form of an emulsion, without theloss of polishing power which is characteristic of other powders in thepresence of waxes or oils. However, water or a water-miscible liquidmust be present in the vehicle in order to obtain satisfactory results.Of all of the vehicles tried, three compounds gave polishingcompositions with the Silene" which were outstanding in their ability toproduce haze-free surfaces with a minimum of rubbing. These vehicles,which are illustrated in the examples, are ethylene glycol, formamidand. glycerol.

This application is a division of our co-pending U. S. ApplicationSerial No. 415,212, filed October 16, 1941.

We claim:

1. A polishing composition characterized by its ability to produce ahaze-free, glossy surface on non-thermoplastic resinous finishes, whichcomprises a vehicle containing essentially a liquid polyhydric alcoholof the group consisting of glycerol and ethylene glycol, and a.polishing abrasive dispersed in the liquid consisting essentially of ahydrated calcium silicate powder containing about 18% by weight CaO, 64%by weight S102, and 14% by weight chemically combined water.

2. A polishing composition characterized by its ability to produce ahaze-free, glossy surface on non-thermoplastic resinous finishes, whichI comprises a vehicle containing essentially a. liquid consisting ofethylene glycol, and a polishing abrasive dispersed in the liquidconsisting essentilaly of a hydrated c alcium silicate powder containingabout 18% by weight CaO, 64% by weight SiOiz, and 14% by weightchemically combined water.

ALBERT SAUNDERS.

LOY S. ENGLE.

